1. Field of the Invention
The present invention relates to manufacturing method and apparatus of a gusset bag having gores on the both sides of the bag.
2. Description of the Related Art
There is conventionally known a three-side-sealed type flat bag container prepared by placing flat films opposed to each other and heat-sealing three sides thereof. When attaching a zipper to this flat bag container, the transfer direction of flat films composing the flat bag container is caused to coincide with the zipper extending direction to improve productivity.
Also for bags other than flat bags, contrivances are made for attaching a zipper. A gusset bag having gores on the both sides of the bag has a wide range of applications because of an excellent capacity. There is therefore a demand for attaching a zipper to the mouth of the gusset bag.
More recently, there is known a gusset bag having a flattened bottom to improve self-standing property of the gusset bag. This gusset bag is called a flat bottom bag, and manufactured by attaching a bottom film to the bag main body having gores.
However, the manufacturing method of the gusset bag requires forming gores on the sides. If the transfer direction of the flat films forming the front and back surfaces of the gusset bag is caused to coincide with the transfer direction of the side films forming the sides of the gusset bag, these directions are different from the zipper extending direction or the bottom film extending direction, resulting in a problem of a poor productivity. The gusset bags are classified into three kinds: a type having a zipper attached thereto, a type having a flat bottom, and a type having a bottom and a zipper attached thereto. It is necessary to use different manufacturing methods in order to manufacture the individual types, and this has resulted in a poor productivity.
Accordingly, it is an object of the present invention to provide manufacturing method and apparatus of a gusset bag capable of coping with various types of gusset bags and permitting improvement of productivity.
The present invention will now be described. For the purpose of solving the aforementioned problems, the present inventor inserted a side film extending in a direction perpendicular to the transfer direction of the flat film between a pair of flat films forming the front and back surfaces of the gusset bag, and folded the both ends of the side film so as to facilitate attachment of the zipper or the bottom film. More specifically, a first aspect of the present invention provides a manufacturing method of a gusset bag having front and back surfaces composed of a pair of flat surfaces opposed to each other, and sides composed of pleat-shaped side surfaces connecting the side edges of the both flat surfaces and tucked in the both flat surfaces. The manufacturing method comprises a step of separating and transferring a pair of flat films for forming the pair of flat surfaces of the bag; a step of inserting side films between the pair of flat films and forming the side surfaces of the gusset bag; a step of forming a strip-shaped film by putting the pair of flat films opposed to each other; a step of sealing the flat films and the side films; a step of forming an open surface at least at an end of the side films and the flat films by tucking in the side film at a gore crease from a point on the crease selected as a base point to an end of the side film in a direction counter to the original tucking direction, and tucking in the side film at lines connecting the two corners at ends of the side film or the proximity thereof and the base point in an inward direction of the gusset bag to form a convex edge, thereby forming an open surface at least at an end of each of the side film and the flat film; and a step of cutting the strip-shaped film along a prescribed cutting line.
According to this aspect of the invention, in which the ends of the side film are folded and an open surface is formed at least at an end of the side films and the flat films, it is possible: (1) to manufacture a gusset bag having a zipper by attaching the zipper onto the end of each flat film; (2) to manufacture a gusset bag having a flat bottom by attaching a bottom film onto the end of each flat film; and (3) to manufacture a gusset bag having a zipper and a flat bottom by attaching the zipper onto one end of each flat film and the bottom film onto the other. There are thus available the manufacturing methods capable of coping with the three types of gusset bag, respectively. Because the transfer direction of the flat film is perpendicular to the extending direction of the side film, the transfer direction of the flat film can be caused to coincide with the transfer direction of the zipper or the transfer direction of the bottom film, thus facilitating attachment of the zipper or the bottom film, and permitting improvement of productivity.
A second aspect of the invention provides a manufacturing method of a gusset bag, further comprising a step of attaching a zipper extending in a direction in parallel with the transfer direction of the flat film to the open surface; and a step of sealing together the zipper and the flat film.
According to this aspect of the invention, it is possible to manufacture a gusset bag having a zipper attached thereto. Since the ends of the side film are folded to form an open surface as described above, it is easier to attach the zipper, and the side film reinforced by the open surface becomes harder to be broken.
A third aspect of the invention provides a manufacturing method of a gusset bag, further comprising a step of attaching, to the end of each flat film, a V-shaped bottom film which extends in a direction in parallel with the transfer direction of the flat film and forms a bottom surface of the gusset bag; and a step of sealing together the bottom film and the flat film.
According to this aspect of the invention, a gusset bag with a flat bottom can be manufactured by attaching a V-shaped film to the depth onto the open surface formed by folding the side film as described above, thus permitting improvement of productivity of gusset bags.
A fourth aspect of the invention provides a manufacturing method of a gusset bag, wherein the open surfaces is formed at the both ends of the side film and the flat film; and the strip-shaped film is cut along a prescribed cutting line so as to form gusset bags in two rows to the left and the right.
According to this aspect of the invention, it is possible to manufacture gusset bags in two rows symmetrically to the right and left in the transfer direction of the flat films, thus permitting improvement of the gusset bag.
A fifth aspect of the invention provides a manufacturing method of a gusset bag, wherein the open surface is formed at the both ends of the side film and the flat film; attaching a zipper, to one end of each flat film, extending in a direction in parallel with the transfer direction of the flat film; and attaching, to the other end of each flat film, a V-shaped bottom film which extends in a direction in parallel with the transfer direction of the flat film, and forms a bottom surface of the gusset bag; and a step of sealing together the zipper and the flat film, on the one hand, and the bottom film and the flat film, on the other hand.
According to this aspect of the invention, it is possible to manufacture a zippered gusset bag having a flat bottom, together with the aforementioned advantages.
A sixth aspect of the invention provides a manufacturing method of a gusset bag, wherein the side film forms side surfaces of the gusset bag located in front and back in the transfer direction of the flat film.
According to this aspect of the invention, four side surfaces in total including two rows of left and right side films and front and back side films in each row in the transfer direction are formed. It is thus possible to further improve productivity of gusset bags.
As in any of seventh to ninth aspects of the invention, the side film may be prepared by combining two V-shaped films, or by bending the both sides of a rectangular film so that the both ends of the film are located on the center line of the film, or by crushing a tubular film.
According to tenth aspect of the invention, the side film is composed by combining boat-shaped films prepared by folding a rectangular film at the center line, forming a bottom crease, tucking in the film at the crease from a point on the crease selected as a base point to an end of the film in a direction counter to the original tucking direction, and tucking in the film at lines connecting the two corners at ends of the film or the proximity thereof and the base point in an inward direction of the gusset bag to form a convex edge. In the step of forming the open surface, it is not necessary to fold the side film to form the open surface on the side film.
According to the eleventh aspect of the invention, there is provided a manufacturing apparatus of a gusset bag having front and back surfaces composed of a pair of flat surfaces opposed to each other, and sides composed of pleat-shaped side surfaces connecting the side edges of the both flat surfaces and tucked in the both flat surfaces, comprising a transfer unit for separating and transferring a pair of flat films for forming the pair of flat surfaces of the bag; a side film inserting unit for inserting side films between the pair of flat films so as to extend in a direction perpendicular to the transfer direction of the flat films; a film placing unit for forming a strip-shaped film by placing the pair of flat films opposed to each other; a side film sealing unit for sealing the flat films and the side films; an open surface forming unit for forming an open surface at least at an end of the side films and the flat films by tucking in the side film at the gore crease from a point on the crease selected as a base point to an end of the side film in a direction counter to the original tucking direction, and tucking in the side film at lines connecting the two corners at ends of the side film or the proximity thereof and the base point in an inward direction of the gusset bag to form a convex edge; thereby forming an open surface at least at an end of each of the side film and the flat film; and a cutting unit for cutting the strip-shaped film along a prescribed cutting line, thus solving the aforementioned problems.
According to this aspect of the invention, there is available a manufacturing apparatus of a gusset bag coping with the above-mentioned kinds of gusset bags.